Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With readOnlyHint=false and destructiveHint=false the annotations only say 'write, but safe'; the description adds the crucial nuance that no bytes are uploaded and no generation starts here, so the agent understands the actual side effect is only URL generation. It doesn't mention presigned-URL expiry or upload constraints (size, content-type enforcement), which would be the remaining behavioral gaps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the action, followed by the when-to-use and the exclusion. Every sentence carries distinct information; no repetition of the title or schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be spelled out, and the description still names the two key outputs (upload_url, file_path). Combined with the workflow guidance and the non-mutation clarification, an agent has everything needed to call this correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, with per-field descriptions, enum values, extension pattern and the ordering guarantee all documented in the schema. The description adds only the general notion of 'file-path pairs' and does not extend parameter meaning, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Creates presigned upload URL and file-path pairs for local media') and immediately distinguishes the tool from the many create_* siblings by naming what it does not do ('Does not upload file bytes or start a generation'). An agent can place it correctly without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit trigger ('Use when a generation needs a file the user has locally'), concrete next steps (upload raw bytes to upload_url, then pass file_path to the create tool), and a negative condition ruling out the most likely misuse. Nothing is left to inference about when to pick this over create_video_from_image or similar.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.